This invention relates to a device for bridging the gap or opening between two composite parts of roofing. The device consists of an expansion joint strip, the center section of which is made of a rubber elastic material and is placed in the joint, while the two side sections, being made of sheet metal to which the edges of the center section are vulcanized in a waterproof manner, are adhered to the portions of the roofing on either side of the joint. The invention further relates to a method of testing the device for tightness.
Device of the foregoing type are known from Swiss Patent CH-PS No. 456.106 (METOBA ANSTALT) and are sold commercially under the generic term of "dilatation element".
Although dilatation elements of this type have proven their merit a hundred thousand times, defects do occasionally occur and they may have a variety of causes. In addition to defects caused by mechanical damage, chemical decomposition, disintegration due to the impact of UV radition, and production errors in the vulcanization process resulting in the formation of blisters and insufficient adhesive properties, the majority of defects that occur are due to improper installation.
Since the causes for the various defects are known, a number of suggestions to avoid damage have been made in the past. In particular, suggestions have been advanced to guard against mechanical and chemical destruction and against the effects of ultraviolet radiation. The following publications deal with matters of this kind: DE-OS No. 17 59 246 (Schoop), DE-GM No. 70 44 967 (Wetra-Trachsel & Co.) and DE-OS No. 20 18 309 and DE-AS No. 25 31 695 (E. Ammann AG). The German Pat. No. 25 31 695 corresponds to U.S. Pat. No. 4,071,994.
No protection, however, has so far been available against faulty installation. In particular, the careless handling of blow torches has been found time and again to be the cause of damage to the rubber elastic center section. This has given rise to the need to inspect the expansion joint element after completion of the installation.
German public disclosure DE-OS No. 41 365 (Schoop) proposes a detachable cover or lid to make visual inspection possible in the event of damage. To this end, the cover needs to be detached from the dilatation element proper and later be returned to it and reattached by cementing or soldering. Quite apart from the fact that the rubber elastic center portion may easily be destroyed as the cover is reattached to the dilatation element, this prior art proposal, as previously mentioned, merely affords a visual inspection from above. Frequently, however, an unsatisfactory adhesion of the rubber elastic material forming the center section to the sheet metal side sections is invisible to the eye. This is particularly true of detachments occurring at the under side of the sheet metal sections, and where leaking is caused by blister formation in the rubber elastic center section. It was to overcome these defects that the present invention was conceived.